His departure, which has been under discussion for some time, is unsurprising given that the PCC will almost certainly be reconstituted.

Abell, who has spent more than 10 years with the commission, has been in charge during its most difficult period, culminating in the controversy over phone hacking.

He oversaw the early departure of its previous chair, Lady Buscombe, and has worked alongside her successor, Lord Hunt, since his arrival in October last year.

Hunt said he and Abell had agreed that they would work together until they "were in a position to propose a new structure for self-regulation of the press." He added:

"I have valued Stephen's assistance in this, and his professionalism in leading the PCC's staff as they continued their important work...

It is testament to him that the service to complainants, both those in the public eye and those without claim to celebrity, has improved and expanded over the last few years. I wish him success in all his future endeavours."

He said: "I decided last year that it was time for a new challenge. First, I wanted to work with David Hunt in the development of positive proposals for a new structure of self-regulation... I also wanted to give a full account of the work of the PCC to Lord Justice Leveson."

He said he remained "a firm supporter of enhanced self-regulation for the press", adding:

"My greatest professional satisfaction at the PCC has been in our establishment of a bespoke 24-hour service to help complainants obtain redress, stop harassment and prevent the publication of inaccurate or intrusive material.

I leave a great team of people, who have much to offer in the changing world ahead."

It appears that Abell's PCC job, as its is currently constituted, may not be filled. Instead, the commission has appointed Michael McManus to be "director of transition."

McManus, pictured left, has been a long-time associate of Hunt's. They worked together for six years at the law firm Beachcroft, where he dispensed political and legislative advice to clients.

McManus spent years as a special adviser in parliament and also ran Edward Heath's Westminster private office. Most recently he has worked at the PR firm Bell Pottinger.

McManus said: "I am delighted to be joining the PCC at this crucial juncture in its existence. All my work in journalism and politics has convinced me that self-regulation of the press can and must be made to work.

"I relish the challenge of playing such a senior role in the urgent and crucially important task of creating a new, independent press regulator with real teeth."